Rollup type doors are widely used in many applications for forming a closure over an opening in a building. Rollup type doors are typically characterized by flexible curtain-like closure members which are adapted to be wound onto a rotatable drum for moving the door between a closed position and an open position. Flexible curtain rollup doors do, however, require reinforcement to prevent windloads from blowing the curtain out of opposed guide tracks or channels and through the door opening. Such reinforcements may include plural spaced apart windlock members disposed above the curtain edges, a thickened portion of the opposed edges of the curtain or one or more spaced apart laterally extending windbar members disposed adjacent to the door curtain and guided in opposed guide tracks.
However, in many industrial applications of rollup type doors it is also desirable to provide for releasing the aforementioned windbars or windlocks under impact loads which are often encountered by such doors being impacted by freight-moving vehicles, such as lift trucks, for example. Moreover, such doors are also desirably adapted to release from opposed door edge guides at a predetermined air pressure differential or xe2x80x9cwindloadxe2x80x9d to prevent catastrophic failure of the door and its associated support structure. Flexible curtain type doors have been developed which include windbars or windlocks at opposite lateral edges of the door which provide for completely releasing the door from its opposed guides. However, releasing the door at both side edges from the associated guide structure complicates the requirements for reinserting the door curtain in the guide tracks. Still further, certain prior art doors which are provided with side edge windlocks and also are provided with laterally extending reinforcing or stiffening members, often called windbars, are somewhat complicated.
Various other desiderata have been recognized in industrial rollup doors including improvements in the door bottom edge seal, or so called bottom bar, wherein it is desirable to provide weighting structure operable to assist in pulling the door toward a closed position while at the same time configuring the weighting structure so that it will not damage an object upon which the door may inadvertently close.
Still further, it is desirable to provide an uncomplicated and inexpensive design which still meets all of the desiderata and trouble-free operation for rollup type doors. It is to these ends that the present invention has been developed.
The present invention provides an improved flexible curtain type door and an improved rollup flexible type door, in particular, and wherein the door is operable to maintain a closure over an opening under substantial windloads while also providing for release of the door curtain at one side should forces acting on the curtain be excessive and potentially damaging.
In accordance with one aspect of the invention, a flexible curtain type door is provided with combination curtain stiffening struts or battens and windlocks which are operable to release the curtain along at least one of the curtain side edges from curtain side edge guide structure. In particular, the combination struts and windlocks are preferably operable to release the door curtain at only one lateral side thereof to minimize the requirements of resetting the curtain within the guides while providing sufficient relief from forces acting on the door which would otherwise possibly damage the curtain and/or associated door guide structure.
The present invention also provides an improved curtain and strut guide track section which includes opposed recapture chutes and movable guide track parts which provide guidance for the curtain and strut edges during normal operation of the door but also allow reentry or recapture of the curtain and strut edges if the curtain has been displaced from the guide tracks in either one of opposite directions.
Still further, there is provided a flexible curtain type door, particularly adapted for operation as a rollup door and which includes an improved bottom edge or so-called bottom bar assembly including curtain stiffening members which provide stiffness in opposite directions out of the normal plane of the door curtain but allow deflection in a vertical direction generally in the plane of the door. The invention still further includes a simplified and advantageous motor drive arrangement for rotating a drum on which a door curtain is wound when moving the curtain between open and closed positions.
Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the flexible curtain door of the present invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawings.